I have never had a caffeine “buzz” or any jitters. I can drink espresso 5 minutes before bed and not have it bother me at all. However, if I go without caffeine, I have some symptoms. I get very bad headaches, sometimes I shake, I can’t focus, etc. I think it’s because (I am positive of this, actually) I drink a whole lot of caffeine (I am in grad school – it comes with the territory). I have been drinking excessive amounts of caffeine for many years (I drink about a six pack of diet coke and two cups of coffee a day).